In a typical inkjet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol, or mixtures thereof.
An inkjet recording element typically comprises a support having on at least one surface thereof one or more ink-receiving or image-forming layers, and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support.
In order to achieve and maintain high quality images on such an inkjet recording element, the recording element must exhibit no banding, bleed, coalescence, or cracking in inked areas; exhibit the ability to absorb large amounts of ink (including carrier liquid) and dry quickly to avoid blocking; exhibit high optical densities in the printed areas; exhibit freedom from differential gloss; exhibit high levels of image fastness to avoid fade from contact with water, fade from radiation by daylight, tungsten light, or fluorescent light, or fade from exposure to gaseous pollutants; and exhibit excellent adhesive strength so that delamination does not occur.
An inkjet recording element that simultaneously provides an almost instantaneous ink dry time and good image quality is desirable. However, given the wide range of ink compositions and ink volumes that a recording element needs to accommodate, these requirements of inkjet recording media are difficult to achieve simultaneously.
Inkjet recording elements tend to fall into broad categories, porous media and non-porous or swellable media. A typical swellable inkjet recording element from the prior art comprises a topcoat ink-receiving layer containing hydroxypropylmethyl cellulose, poly(vinyl alcohol) and/or polyurethane. Such a topcoat layer is typically applied to a surface of a base layer, using a solvent that is subsequently removed by drying, and is specially formulated to provide ink receptive properties.
Hence, current methods for applying water-soluble polymers onto substrates involve dissolving the polymers and other additives in a carrier fluid to form a coating solution. Suitable carrier fluids may comprise organic solvents and/or water. The coating solution is then applied to the substrate by a number of coating methods, such as roller coating, wire-bar coating, dip coating, air-knife coating, curtain coating, slide coating, blade coating, doctor coating, and gravure coating. In some instances, the coating solution may be extruded as a solution using a slot-die.
The major disadvantage with using such conventional coating methods is that an active drying process is required to remove water or solvent from the coating after the coating has been applied to the substrate. Typically, these drying processes use thermal ovens, and there is a limited choice of substrates that can be conveniently dried in such ovens. Many substrates do not have adequate thermal resistance. These drying processes can also place the ink-jet media manufacturer at a competitive cost disadvantage. For example, the speed of a media manufacturing line is limited by the slow drying rate of the coatings. The cost problems are compounded when multiple coatings, requiring multiple drying steps, are applied to the media.
Besides the manufacturing limitations, the media produced by conventional coating methods are known to lack durability and, because most topcoat formulations contain water-soluble components and, thus, are also sensitive to moisture, so that the use, after printing, of a protective overlaminate layer or the like may be desirable. Additionally, the level of active components in the topcoat formulation can be limited by the viscosity of the topcoat formulation that can be handled in the coater. As a result, the efficiency of the topcoat is commonly increased by increasing the layer thickness, which is known to introduce increased costs and coat weight inconsistencies, which inconsistencies are undesirable because they can adversely affect the performance of the final product.
In contrast to solvent coating, hot-melt extrusion coating technology is a high-speed process. Extrusion coating technology is conventionally used in the packaging industry. In such coating processes, hot-melt extrudable compositions that contain little or no organic solvents or water, are extruded onto a substrate. By employing various thermoplastic resins, such as polyolefins and ethylene copolymers, extrusion coatings can provide strength, moisture vapor barriers, oxygen barriers, gas permeability, abrasion resistance, flame retardancy, flexibility, and elasticity for packaging and other industrial products.
In an effort to avoid the above-mentioned adverse consequences of the conventional coating methods for the manufacture of inkjet recording elements, melt extrusion of ink-receiving layers has been tried. However, in the case of non-porous or swellable ink-receiving layers, many water-soluble polymers, such as high molecular weight polyvinyl pyrrolidone, polyvinyl alcohol, natural polymers, and gums, are not suitable for forming hot-melt extrudable compositions, because these materials tend to degrade and decompose at their melting point temperatures. Hydrophilic thermoplastic polymers tend to decompose at the higher temperatures typically employed in melt extrusion. Hydrophilic materials are also so difficult to extrusion coat because they have poor melt strength. Thus, melt extrusion of ink-receiving layers has had limited use.
U.S. Pat. No. 6,726,981 to Steinbeck et al. relates to a recording material for inkjet printing having an extruded polymer layer that comprises a polyether group-containing thermoplastic copolymer, including polyether amide block copolymers having a polyamide segment and a polyether segment. Further thermoplastic polymers in mixture with the copolymer are listed including polyolefins, ethylene copolymers, polyesters, polycarbonates, polyurethanes, and/or extruded polyvinyl alcohol homopolymers and copolymers, wherein the thermoplastic polymers can be present in the amount of 1 to 50 weight percent based on the polymer mixture. The inkjet recording element can further have an ink-absorbing layer applied as an aqueous solution or dispersion.
U.S. Pat. No. 6,403,202 to Gu et al. discloses a recording material for inkjet printing having an extrudable polyvinyl alcohol containing layer which is extruded on raw base paper, and an ink-receiving layer which is applied as an aqueous dispersion or solution. The patent discloses the optional addition of other polymers (without specifying amounts), which list includes polyurethanes, polyolefins, ethylene copolymers, polyalkylene oxides, polycarbonates, polyesters, polyamides and polyesteramides.
U.S. Pat. No. 6,623,841 to Venkatasanthanam et al. discloses an ink receptive layer that is formed from a melt processable blend of a water-soluble polymer and a substantially water-insoluble polymer, in the amounts, respectively, of 20 to 80 weight percent for each polymer. Preferred water-soluble polymers include polyvinyl alcohols and polyalkyloxazolines. The substantially water-insoluble polymer component of the blend is selected from polyolefins, polyesters, polystyrenes, and mixtures thereof. A particularly preferred alcohol/aliphatic polyester blend is one that comprises 20 to 80 percent by weight of each polymer. A particularly preferred alcohol/polyester blend comprises approximately 60 percent by weight of the aliphatic polyester and approximately 40 percent by weight of the polyvinyl alcohol.
U.S. Pat. No. 6,793,860 to Xing et al. discloses a method for making ink-jet recording media using hot-melt extrudable ink-receptive compositions. The melt-extrudable compositions comprise a blend of a melt-extrudable polyvinyl alcohol composition and, in addition, poly(2-ethyl-2-oxazoline), a hydrolyzed copolymer of ethylene and vinyl acetate, ethylene/acrylic acid copolymers, or ethylene/methacrylic acid copolymers.
The above-mentioned patents are not directed to extruded voided image-receiving layers. However, inkjet recording elements that employ extruded porous layers that act as suitable ink-receiving layers on one or both sides of a support are also known. For example, U.S. Pat. No. 6,379,780 to Laney et al., U.S. Pat. No. 6,489,008, and U.S. Pat. No. 6,409,334 to Campbell et al. the disclosures of which are hereby incorporated by reference, discloses an inkjet recording element comprising an ink-permeable polyester substrate comprising a base polyester layer and an ink-permeable upper polyester layer, the upper polyester layer comprising a continuous polyester phase having an ink absorbency rate resulting in a dry time of less than about 10 seconds and a total absorbent capacity of at least about 14 cc/m2, the substrate having thereon a porous image-receiving layer having interconnecting voids.
U.S. Pat. No. 5,443,780 to Matsumoto et al. discloses the use of an oriented film of polylactic acid and methods for producing the same. U.S. Pat. No. 5,405,887 to Morita et al. discloses breathable, hydrolysable, porous films made by a process comprising adding finely powdered filler having an average particle size of 0.3 to 4 μm to a polylactic acid based resin. Such films are described as useful as a material for leak proof films of sanitary materials and packaging materials. Such materials are, therefore, not open-pore in nature.
Commonly assigned U.S. Ser. No. 10/722,886 to Laney et al., hereby incorporated by reference in its entirely, discloses an inkjet recording element comprising an ink-permeable microvoided layer comprising a continuous phase that is a polylactic-acid-based material.
Commonly assigned U.S. Ser. No. 10/742,164 to Campbell et al., hereby incorporated by reference in its entirely, discloses an inkjet recording element comprising a porous ink-receiving layer over and adjacent to an ink-permeable microvoided substrate layer comprising a polyester ionomer, said substrate layer comprising 5 to 70 percent by weight solids of a neutral polyester; 5 to 40 percent by weight solids of a polyester ionomer; and 25 to 65 percent by weight of a voiding agent, wherein the microvoided substrate layer and the porous ink-receiving microvoided layer both having interconnecting voids. In one preferred embodiment of the invention, the ink-permeable polyester microvoided substrate layer comprises sulfonated polyester and the ink-permeable microvoided layer comprising a continuous phase is a polylactic-acid-based material.
U.S. Pat. No. 6,790,491 to Sebastion et al. discloses a biaxially oriented, melt-processed image-receptive film comprising an immiscible blend of at least one semicrystalline polymer component, at least one ink absorptive polymer component, and at least one inorganic filler. However, this inkjet recording element is designed for solvent-based inks, not aqueous inks as intended to be used with the present invention.
It is an object of this invention to provide an inkjet recording element that has a fast ink dry time. It is another object of this invention to provide an inkjet recording element that provides a more robust material for a support.
Extrusion of an image-receiving layer for an inkjet recording element is an economical method of manufacture, but compared to common coating techniques, it is difficult to achieve the desired properties of an image-receiving layer for use in inkjet recording. There are many unsolved problems in the art and many deficiencies in the known products, which have severely limited their commercial usefulness. A major challenge in the design of an image-recording element is to provide improved picture life, a critical component of which is resistance to light fade.
It would be desirable to have new methods for making ink-jet recording media that are capable of forming high-quality, multicolored images with aqueous-based inks from inkjet printers. The present invention provides such methods and the resulting media. It is an object of this invention to provide a multilayer inkjet recording element that has excellent image quality and improved picture life. It would be desirable to obtain low ozone fade in an instant dry media.